Solid-state lighting is an attractive alternative to incandescent and fluorescent lighting systems for backlighting of translucent panels or materials and signs because of its relatively higher efficiency, robustness, and long life. A number of LED-based backlighting systems have been used, but these generally suffer from one or more deficiencies. It is often desirable to have the thickness of the panel or sign as small as possible, for example to fit within a restricted space, to provide a thin visual perspective, or to reduce cost. Current LED systems generally include LEDs that are operated at relatively high current, resulting in very bright light sources that must be mixed and diffused to provide even and low-glare illumination of the panel or sign. For systems having LEDs spaced several inches or more apart, this may result in an undesirably large spacing between the LEDs and the diffuser. The diffuser reduces the efficiency, and as the LEDs become brighter, more diffusion, with concomitant decreasing efficiency, is required to achieve a homogeneous luminance across the panel or sign. Furthermore, such systems often require relatively large heat sinks or thermal management systems, which also take up space and may require suitable ventilation, for example passive ventilation or active ventilation such as fans, to prevent deleterious heat buildup. These issues typically lead to undesirably large, thick, and potentially complicated lighting systems.
In addition, many applications for backlighting and illuminated panels and signs require custom sizing to fit in a particular location. Systems consisting of relatively few high-brightness LEDs on rigid circuit boards or systems employing edge-lit panels may be difficult to use cost-effectively in a wide range of installations, e.g., installations requiring size customization while maintaining high illumination uniformity and high efficiency.
Accordingly, there is a need for solutions that provide LED-based lighting systems having a thin form factor with improved uniformity, high efficiency, and which are simple to install.